Resistance change memory device and fabrication method thereof

ABSTRACT

The resistance change memory device including a first resistance change memory element, a second resistance change memory element, and a memory controller is provided. The first resistance change memory element is disposed on a chip. The second resistance change memory element is disposed on the same chip. The memory controller is disposed on the same chip. The memory controller is configured to control data access of the first resistance change memory element and the second resistance change memory element. An accessing frequency of the first resistance change memory element is different from an accessing frequency of the second resistance change memory element.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. application Ser.No. 15/379,505, filed on Dec. 15, 2016, now allowed. The entirety of theabove-mentioned patent application is hereby incorporated by referenceherein and made a part of this specification.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The invention generally relates to a memory device and a fabricationmethod thereof, in particular, to a resistance change memory device anda fabrication method thereof.

2. Description of Related Art

The performance of resistance change memory is highly dependent on thecomposition of the phase change material. Relying on a singlecomposition, such as the originally popular Ge₂Sb₂Te₅ (GST), makes theresistance change memory difficult to simultaneously satisfy retentionand speed requirements. On the other hand, the recent improvements inthe resistance change memory technology and the rise of 3D XPoint™memory suggests this technology cannot be ignored just yet, and anoptimized form may be quite competitive against both dynamic randomaccess memory (DRAM) and NAND flash, mainly due to the enhancedcrosspoint density avoiding the processing of small transistors.

SUMMARY OF THE INVENTION

Accordingly, the invention is directed to a high-density crosspointmemory for high-speed and storage functions.

An exemplary embodiment of the invention provides a resistance changememory device. The resistance change memory device includes a firstresistance change memory element, a second resistance change memoryelement, and a memory controller. The first resistance change memoryelement is disposed on a chip. The second resistance change memoryelement is disposed on the same chip. The memory controller is disposedon the same chip. The memory controller is configured to control dataaccess of the first resistance change memory element and the secondresistance change memory element. An accessing frequency of the firstresistance change memory element is different from an accessingfrequency of the second resistance change memory element.

In order to make the aforementioned and other features and advantages ofthe invention comprehensible, several exemplary embodiments accompaniedwith figures are described in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

FIG. 1 illustrates a block diagram of a resistance change memory deviceaccording to an embodiment of the invention.

FIG. 2 to FIG. 6 and FIG. 7A to FIG. 11A are cross-sectional viewsillustrating a fabricating process of a resistance change memory deviceaccording to an embodiment of the invention.

FIG. 7B to FIG. 11B are top views illustrating the fabricating processof the resistance change memory device depicted in FIG. 7A to FIG. 11Aaccording to an embodiment of the invention.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numbers areused in the drawings and the description to refer to the same or likeparts.

For the sake for clarity, sizes and relative sizes of each layer shownin the drawings may be exaggerated.

Resistance change memory's recent developments show substantial progressin reliability and performance improvement. It is evident that choosingcomposition is a tradeoff between retention and speed. A key emphasis ofexemplary embodiments of the invention is to have one part of theresistance change memory used for high-speed operation, where retentionis not important, and the other part for storage, not requiring suchhigh speed operation.

The exemplary embodiments of the invention are to use two or even threedifferent resistance change memory compositions for differently weightedmemory functions. A phase change material with higher crystallizationtemperature is more suitable for storage since its high-temperatureretention is better, while another phase change material with lowercrystallization temperature or higher crystallization speed is betterfor working memory with low latency, like DRAM.

Additionally, a third type of resistance change memory composition maynot even allow crystallization under all expected thermal environments.These compositions still can switch ON by threshold switching but do notretain their ON state after the current is shut off, allowing them to beideal switches or access devices.

A DRAM-NAND combination (MCP or NVDIMM) may therefore be realized on onechip with the use of cross-point resistance change memory arrays of twodifferent resistance change memory compositions, one for the morevolatile memory, one for storage, along with a common third compositionfor threshold switching, or alternatively, a different crosspointselector device, e.g., diode, for use as access devices in thecrosspoint arrays. The high-speed memory array may be significantlydifferent density from the storage array, e.g., 4-16 Gb vs. 128-512 Gb.

The crosspoint array fabrication for two different resistance changememory compositions would require a particular sequence that could addtwo masks to the conventional crosspoint array fabrication flow. Forbetter understanding of the invention, at least one exemplaryembodiments of the invention are explained below with reference to thefigures.

FIG. 1 illustrates a block diagram of a resistance change memory deviceaccording to an embodiment of the invention. Referring to FIG. 1, theresistance change memory device 100 of the present embodiment includes afirst resistance change memory element 110, a second resistance changememory element 120 and a memory controller 130. In the presentembodiment, the memory controller 130 is configured to control dataaccess of the first resistance change memory element 110 and the secondresistance change memory element 120. In the present embodiment, theresistance change memory device 100 may be a phase change memory device.

In the present embodiment, the access control of memory may beimplemented by using suitable control operations in the related art,which are not particularly limited in the invention. Enough teaching,suggestion, and implementation illustration for access control andembodiments thereof may be obtained with reference to common knowledgein the related art, which is not repeated hereinafter.

In the present embodiment, the first resistance change memory element110, the second resistance change memory element 120 and the memorycontroller 130 are disposed on the same chip. In one embodiment, thefirst resistance change memory element 110 is configured for high-speedoperation, e.g. a working memory, and the second resistance changememory element 120 is configured for storage, e.g. a storage memory.Accordingly, the accessing frequency of the first resistance changememory element 110 is higher than the accessing frequency of the secondresistance change memory element 120.

In the present embodiment, the first resistance change memory elementincludes a first phase change material, and the second resistance changememory element includes a second phase change material. In anembodiment, the first phase change material may be a fast-crystallizingSbTe-based phase change material, e.g. 2% N in SbTe and the second phasechange material may be a slow-crystallizing Ge-rich GST phase changematerial, e.g. 5% Ge in SbTe. Accordingly, the crystallization speed ofthe first phase change material is faster than the crystallization speedof the second phase change material. The phase change materials are notintended to limit the invention.

FIG. 2 to FIG. 6 and FIG. 7A to FIG. 11A are cross-sectional viewsillustrating a fabricating process of a resistance change memory deviceaccording to an embodiment of the invention. FIG. 7B to FIG. 11B are topviews illustrating the fabricating process of the resistance changememory device depicted in FIG. 7A to FIG. 11A according to an embodimentof the invention. Referring to FIG. 2 to FIG. 11B, FIG. 2 shows a basicsubstrate 200 and starting layers 210. In the present embodiment, thestarting layers 210 includes a word line layer 410, a bottom electrodelayer 420, a switch layer 430, a middle electrode layer 440, and adielectric layer 212. In the step depicted in FIG. 2, the word linelayer 410, the bottom electrode layer 420, the switch layer 430, themiddle electrode layer 440, and the dielectric layer 212 aresequentially formed on the substrate 200. Accordingly, the startinglayers 210 are formed on the substrate 200. In an embodiment, the layerstructure 214 may be p-n junction layers.

FIG. 3 and FIG. 4 show an etched area for the first memory functionblock, depositing a resistance change memory stack for the first memoryfunction, and planarization. In FIG. 3 and FIG. 4, an area is etched inthe dielectric layer 212, and a first resistance change memory stack 112is deposited to the etched area. In the present embodiment, the firstresistance change memory stack 112 includes a first phase changematerial layer 310 and a top electrode layer 320. The first phase changematerial layer 310 and the top electrode layer 320 are sequentiallyformed on the dielectric layer 212. Next, the first phase changematerial layer 310 and the top electrode layer 320 outside of the etchedarea are removed to planarize the dielectric layer 212. The firstresistance change memory stack 112 in the dielectric layer 212 areformed for the first resistance change memory element 110.

FIG. 5 and FIG. 6 show an etched area for the second memory functionblock, depositing another resistance change memory stack for the secondmemory function, and planarization. In FIG. 5 and FIG. 6, an area isetched in the dielectric layer 212, and a second resistance changememory stack 122 is deposited to the etched area. In the presentembodiment, the second resistance change memory stack 122 includes asecond phase change material layer 510 and a top electrode layer 520.The second phase change material layer 510 and the top electrode layer520 are sequentially formed on the dielectric layer 212. Next, thesecond phase change material layer 510 and the top electrode layer 520outside of the etched area are removed to planarize the dielectric layer212. The second resistance change memory stack 122 in the dielectriclayer 212 are formed for the second resistance change memory element120. Two masks are used so far. The crosspoint fabrication flow follows,which uses an X-line mask and a Y-line mask.

In the present embodiment, at least two phase-change chalcogenidecompositions are utilized, and possibly a third (without phase-change)for threshold switching. The material of the switch layer 430 may beGeTe6, for example, but the invention is not limited thereto. For theetching of the different compositions it is preferred to use Clchemistry since it demonstrates the fastest etch for the Sb-richhigh-speed and Ge-dominant storage composition. However a morefluorine-based chemistry may be added to etch the Te-rich selectorcomposition, which is common to both the high-speed and storagecrosspoint memory blocks anyway.

FIG. 7A schematically shows an etch word line pattern in a specificdirection, e.g. the Y direction. FIG. 7B illustrates the fabricatingprocess of the resistance change memory device depicted in FIG. 7A. FIG.8A schematically shows dielectric backfill and planarization. FIG. 8Billustrates the fabricating process of the resistance change memorydevice depicted in FIG. 8A. Referring to FIG. 7A to FIG. 8B, the wordingpattern 710 is formed, so that a space is generated between the wordingpattern 710. Next, the dielectric material is backfilled to the spacebetween the wording pattern 710, and the dielectric layer 212 is furtherplanarized.

FIG. 9A schematically shows that bit line contacts are etched. FIG. 9Billustrates the fabricating process of the resistance change memorydevice depicted in FIG. 9A. FIG. 10A is a cross-sectional view along theline A1-A2 depicted in FIG. 10B, and schematically shows that the bitline pattern is etched. FIG. 10B illustrates the fabricating process ofthe resistance change memory device depicted in FIG. 10A. FIG. 11A is across-sectional view along the line A3-A4 depicted in FIG. 11B, andschematically shows the pattern between the bit lines. FIG. 11Billustrates the fabricating process of the resistance change memorydevice depicted in FIG. 11A. Referring to FIG. 9A to FIG. 11B, bit linecontacts 910 are formed on the substrate 200, where the bit linecontacts 910 pass through the starting layers 210. Next, the bit linepattern 720 on the dielectric layer 212 is formed, where the bit linepattern 212 contacts the bit line contacts 910. In FIG. 11A, theetched-out areas marked by the dotted lines may be backfilled bydielectric materials again.

In summary, in the exemplary embodiment of the invention, one part ofthe resistance change memory used for high-speed operation, whereretention is not important, and the other part for storage, notrequiring such high speed operation. A cost advantage is expected to berealized since although 5 back end of line (BEOL) masks, e.g. high-speedblock, storage block, word lines, bit line contact, bit lines are addedwith processing, the Flash and DRAM array FEOL steps (>10 masks withprocessing) are no longer needed. Additionally, the periphery CMOSfront-end-of-lines (FEOL) are fabricated under the crosspoint array,further saving chip area.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of theinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the invention covermodifications and variations of this invention provided they fall withinthe scope of the following claims and their equivalents.

What is claimed is:
 1. A resistance change memory device, comprising: afirst resistance change memory element disposed on a chip; a secondresistance change memory element disposed on the same chip; and a memorycontroller disposed on the same chip, and configured to control dataaccess of the first resistance change memory element and the secondresistance change memory element, wherein an accessing frequency of thefirst resistance change memory element is different from an accessingfrequency of the second resistance change memory element, wherein thefirst resistance change memory element comprises a first phase changematerial, the second resistance change memory element comprises a secondphase change material, and the accessing frequency of the first phasechange material is different from the accessing frequency of the secondphase change material.
 2. The resistance change memory device accordingto claim 1, wherein the accessing frequency of the first resistancechange memory element is higher than the accessing frequency of thesecond resistance change memory element.
 3. The resistance change memorydevice according to claim 1, wherein the first phase change material isdifferent from the second phase change material.
 4. The resistancechange memory device according to claim 3, wherein a crystallizationspeed of the first phase change material is faster than acrystallization speed of the second phase change material.
 5. Theresistance change memory device according to claim 3, wherein the firstphase change material is Ge-rich GeSbTe (GST) material, and the secondphase change material is a SbTe-based material.